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Proceedings Paper

Analysis of stress-driven delamination in contact vias
Author(s): Martha Small; Doug Crook; Eric Nikkel; David Buck
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Paper Abstract

During the development of a 0.5 micrometer plug process (0.8 micrometer contacts), high temperature operating life tests for reliability indicated a failure mechanism caused by open contacts at contacts 2 and higher. Scanning electron microscope (SEM) images of cross-sections of opened contacts showed that the upper surface of the metal line was delaminating from the upper TEOS oxide and the tungsten plug. Further investigation revealed that delamination occurs even prior to W deposition, indicating that the real problem is with debonding at the top metal (TiW)-TEOS interface. Other symptoms of the problem are that it depends on contact geometry (contact size and enclosure) and is zonal. The extent of bad contacts also is sensitive to the type of etch used at contact resist strip; the situation improves when NOE is replaced by the milder ST22 strip. All of these symptoms can be understood in terms of stress- driven delamination at a poorly bonded interface. In this paper we present experimental results which show the effects of TEOS stress, film thickness, TEOS chamber 'season' (interfacial chemistry), metal surface treatments and contact resist strip on contact integrity. A model based on finite element calculations is presented that relates TEOS stress and contact geometry to the observed behavior. Following these findings, process changes were put in place to improve adhesion and to prevent notching (crack initiation) at the metal-oxide interface. Since adding these steps, the problem has not recurred.

Paper Details

Date Published: 12 September 1996
PDF: 12 pages
Proc. SPIE 2874, Microelectronic Manufacturing Yield, Reliability, and Failure Analysis II, (12 September 1996); doi: 10.1117/12.250833
Show Author Affiliations
Martha Small, Hewlett-Packard Co. (United States)
Doug Crook, Hewlett-Packard Co. (United States)
Eric Nikkel, Hewlett-Packard Co. (United States)
David Buck, Hewlett-Packard Co. (United States)

Published in SPIE Proceedings Vol. 2874:
Microelectronic Manufacturing Yield, Reliability, and Failure Analysis II
Ali Keshavarzi; Sharad Prasad; Hans-Dieter Hartmann, Editor(s)

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